Recent research has uncovered a stunning revelation about the early history of our planet. Scientists have long believed that it took hundreds of millions of years for the magma oceans of ancient Earth to solidify. However, a groundbreaking new study has shown that this process occurred much more quickly than previously thought, taking only a couple of million years. These findings are shedding new light on the evolution of our planet and challenging existing theories about its formation.
The current scientific consensus is that the Earth formed approximately 4.54 billion years ago, or 4.54 Ga (billion years ago). This age is based on the radiometric dating of rocks and meteorites and other types of evidence. The Earth’s formation began with the accretion of dust and gas in the early solar system, gradually forming into larger bodies through collisions and gravitational attraction. Eventually, these bodies grew large enough to become planetesimals, which then combined to form protoplanets. The protoplanet that would become the Earth grew through collisions and gravitational attraction until it reached its current size.
The process of Earth’s formation was complex and occurred over a long period, but it ultimately led to the formation of a planet uniquely suited to support life. But long before Earth became a haven for life, it underwent hellish transformations. Now, scientists at Florida State University shed light on the ocean of magma that covered ancient Earth and how long it took for it to solidify.
A magma ocean
The study published in Nature Communications revealed that the magma ocean that covered the Earth early in its formation took less than a couple of million years to solidify. This global ocean of magma extended thousands of kilometers into the Earth’s core. The cooling rate of this magma ocean influenced the formation of the different layers of the planet and its chemical composition.
Previous research estimated that it took hundreds of millions of years for that magma ocean to solidify, but the new Florida State University (FSU) study has dramatically reduced these uncertainties “to less than a couple of million years.” According to Mainak Mookherjee, an associate professor of geology in the Department of Earth, Ocean, and Atmospheric Science, the magma ocean has played a significant role in the history of Earth, and this research provides insights into fundamental inquiries about the planet.
How do they know?
But how can scientists possibly know this? As it turns out, when magma cools, it forms crystals. What happens to these crystals depends on how viscous the magma is and the density of the crystals. Denser crystals sink. This, in turn, modifies the composition of the magma. As scientists explain, how fast magma solidifies depends on its viscosity. Less viscous magma enables faster cooling. Thicker magma equals longer cooling. Professor Mookherjee and his colleagues performed simulations that lasted for six months using the high-performance computing facility at the FSU and the National Science Foundation computing facility.
Suraj Bajgain, a former post-doctoral researcher at FSU who is currently a visiting assistant professor at Lake Superior State University, noted that the substantial size of Earth implies that pressure at depth is likely to be exceedingly high. He explained that even if the viscosity of magma at the surface is known, determining the viscosity hundreds of kilometers beneath the surface is a formidable task.
Furthermore, the study sheds light on the origin of the chemical variations observed in Earth’s lower mantle. Earth scientists have long been puzzled by the fact that lava samples from oceanic ridges on the ocean floor and volcanic islands such as Hawaii and Iceland solidify into basaltic rocks that look alike but possess dissimilar chemical properties.